This invention relates generally to on-line sampling of hot effluent gases from high temperature reactors; more specifically, it concerns apparatus and method to achieve efficient on-line sampling of such gases.
There is a continuing need for efficient sampling of hydrocarbons, some of which boil at high temperatures so that they condense in the usual sampling devices which are at lower temperatures. Example of such gases are those produced in the thermal cracking for olefin production of hydrocarbon mixtures such as naptha, gasoil, etc. In such processes, the effluent exits from the cracking coil at around 850.degree. C., and typically proceeds to a transfer line heat exchanger with an outlet temperature of about 340.degree. C. The effluent contains steam, hydrogen and hydrocarbons from methane up to components having as many as 20 carbon atoms. It is of importance to sample and analyse such an effluent at frequent intervals under on-line conditions, to obtain up-to-date information as to composition, rather than obtaining its composition from periodic plant balances.
Prior attempts to achieve analysis of such gases include provision of a device that had to be carried to a remote analytical laboratory after receiving a hot gas sample. This and other devices were plagued by condensation of heavy products, causing unwanted fouling or plugging, and frequently leading to incorrect analysis of the effluent.